Calling the original function when using Ext.override

What I want to do is redefine a function for everyone in BaseField without subclassing it. However, I still want it to do the original functionality without creating a recursive loop, obviously.

I am new to the whole Ext.override concept. I would hate to subclass in this particular case and would love to use the Ext.override feature. I just want to add functionality and not take it away, and I don't even want to think about (*shutters*) copying the source code from the original implementation.